Ubuntu Manpage: kdump-tools.conf - configuration file for the kdump-tools init script

name
synopsis
description
options
usage
examples
files
diagnostics
see also
author

Provided by: kdump-tools_1.5.5-2ubuntu1.6_all

NAME

       kdump-tools.conf - configuration file for the kdump-tools init script

SYNOPSIS

       /etc/default/kdump-tools

DESCRIPTION

       kdump-tools  manages  the  kdump feature of the Linux kernel.  The /etc/default/kdump-tools file contains
       local configuration settings of kdump.

       This file is sourced into a shell script, so it's format should be consistent with shell scripting.

OPTIONS

USE_KDUMP
Controls whether or not kdump-tools will take any action. If not set or 0, the kdump-tools init
script will not run.

KDUMP_SYSCTL
Controls when a panic occurs, using the sysctl(8) interface. Each time a kdump kernel is loaded,
“sysctl -w $KDUMP_SYSCTL” is also executed, thus allowing the system adiminstrator to maintain
customizable conditions for a kdump. The contents of this variable should be the “variable=value
...” portion of the “sysctl -w” command. If not set, “kernel.panic_on_oops=1” will be used.
This feature can be disabled by setting
KDUMP_SYSCTL=“ ”

See sysctl(8) for more info.

KDUMP_KERNEL
A full pathname to a kdump kernel (the kernel that is kexec'd at crash time in a reserved memory
area, exposing the old kernel's memory for dumping). If not set, kdump-config will use the boot
kernel as the kdump kernel if it is relocatable; otherwise you must set KDUMP_KERNEL in order for
kdump-tools to work.

KDUMP_INITRD
A full pathname to the kdump initrd (if used). If KDUMP_KERNEL is set and KDUMP_INITRD is not
set, a warning message will be printed, and an initrd will not be used.

KDUMP_COREDIR
Full path to a directory where the vmcore will be saved. Date stamped subdirectories are created
each time a vmcore file is processed. If not set, /var/crash will be used.

KDUMP_FAIL_CMD
This variable specifies a command to run if the vmcore save fails. If not set, no special action
is taken.

MAKEDUMP_ARGS
Extra arguments passed to makedumpfile(8). If not set, “-c -d 31” will be used. This tells
makedumpfile to use compression, and reduce the corefile to in-use kernel pages only. See
makedumpfile(8) for details.

KDUMP_KEXEC_ARGS
Additional arguments to the kexec command used to load the kdump kernel.

KDUMP_CMDLINE
Normally, the current kernel commandline is obtained from /proc/cmdline. Set this variable to
override /proc/cmdline.

KDUMP_CMDLINE_APPEND
Additional arguments to append to the command line for the kdump kernel. If not set, “irqpoll
maxcpus=1 nousb” will be used.

USAGE

kdump-tools is as automated as can be at this point but there are some prerequisites to using it.
Additionally, some manual configuration is still required.

Manual Configuration
1. USE_KDUMP is set to 0 by default. To enable kdump-tools, edit the /etc/default/kdump-tools
configuration file and set USE_KDUMP=1.

2. Kernel Command line parameters - the kernel must be booted with a crashkernel= command line
parameter. Some example crashkernel parameters:
ia64: crashkernel=384M
x86: crashkernel=128M
x86_64: crashkernel=256M

Some users may also want to add nmi_watchdog=1 on certain systems. The nmi watchdog will cause
the kernel to panic (and kdump) if a system hang is detected.

The kernel command line parameter is generally set in one of these files: /etc/default/grub,
/boot/grub/menu.lst, /etc/elilo.conf, or /etc/lilo.conf. If the command line parameter is
changed, a reboot is required in order for it to take effect.

3. Architectural considerations

A) x86 && PAE && memory > 4 Gigabytes - use KDUMP_KEXEC_ARGS="--elf64-core-headers"

B) x86 and x86_64 - Some systems can take advantage of the nmi watchdog. Add nmi_watchdog=1
to the boot commandline to turn on the watchdog. The nmi interrupt will call panic if
activated.

C) ia64 - Some systems may need KDUMP_KEXEC_ARGS="--noio". Use this if the system hangs after
a panic, but before the kdump kernel begins to boot.

Prerequisites
1. Boot Kernel Configuration - The boot kernel must be configured with CONFIG_KEXEC=y and, if it is
also to be used as the kdump kernel, CONFIG_CRASHDUMP=y.

For ia64, only makedumpfile level 1 will work if the memory model selected is CONFIG_DISCONTIG.
CONFIG_SPARSEMEM is recommended instead.

2. Kdump Kernel Configuration - The kdump kernel must be relocated or relocatable. ia64 is
relocatable by default, but x86, x86_64, and powerpc must be built with CONFIG_RELOCATABLE=y.
Other architectures may require a predermined start location via CONFIG_PHYSICAL_START. If the
boot kernel is relocatable, kdump-tools will automatically use that kernel. Otherwise, a
relocatable or relocated kernel will need to be provided. The kdump kernel can be specified in
the /etc/default/kdump-tools file. Set the KDUMP_KERNEL variable and if necessary the
KDUMP_INITRD variable to point to the provided kernel and its initrd.

The kdump kernel must be configured with: CONFIG_CRASH_DUMP=y

EXAMPLES

       Also panic and kdump on oom:
              KDUMP_SYSCTL="kernel.panic_on_oops=1 vm.panic_on_oom=1"

       Use this option on x86 systems with PAE and more than 4 gig of memory:
              KDUMP_KEXEC_ARGS="--elf64-core-headers"

       This option starts a shell if kdump-tools cannot save the vmcore file:
              KDUMP_FAIL_CMD="/bin/bash; reboot -f"

FILES

       /etc/init.d/kdump-tools  an init script to automatically load a  kdump  kernel,  or  save  a  vmcore  and
                                reboot.

       /etc/default/kdump-tools the kdump-tools configuration file

       /var/crash/kernel_link   a link to the current debug kernel

       /var/crash/kexec_cmd     the last kexec_cmd executed by kdump-config

DIAGNOSTICS

       See kdump-config(8) for explanations of various error messages.

AUTHOR

       Terry Loftin <terry.loftin@hp.com>